On Saturday, Turkey announced a new wave of air strikes in retaliation for two separate attacks on its bases in northern Iraq that killed 12 soldiers, which Ankara blamed on Kurdish militants.

Eight civilians were killed in strikes on Monday, said the Syrian Observatory for Human Rights, revising an earlier toll of six deaths.

The Britain-based monitor, which has a network of sources inside Syria, said five of the victims were employees of a printing works in the northern city of Qamishli, near the Turkish border.

Syrian Kurdish news agency ANHA also reported eight deaths.

The strikes hit more than 20 targets, primarily in the Qamishli area of the semi-autonomous Kurdish administration, the monitor and AFP correspondents in the region said.

Farhad Shani, spokesman for the US-backed, Kurdish-led Syrian Democratic Forces (SDF), said on X, formerly Twitter, that the strikes destroyed "more than 25" civilian facilities and confirmed the death toll of eight civilians.

The SDF spearheaded the battle to dislodge Islamic State group fighters from their last scraps of territory in Syria in 2019.

On Saturday evening, an AFP correspondent as well as the Observatory reported strikes against oil sites near the Turkish border, without reporting any victims.

In October, Turkey intensified air strikes on Syria's northeast after an attack in Ankara that wounded two security personnel earlier that month.

A branch of the Kurdistan Workers' Party (PKK) -- listed as a terrorist group by Ankara and its Western allies -- claimed responsibility for the attack, the first bombing to hit the Turkish capital since 2016.

Turkey views the Kurdish People's Protection Units (YPG) that dominate the SDF as an offshoot of the PKK.

Since 2016, Turkey has carried out successive ground operations to expel Kurdish forces from border areas of northern Syria.

The conflict in Syria has killed more than half a million people since it began in 2011 with the authorities' brutal crackdown on anti-government protests, spiralling into a devastating war involving foreign armies and jihadists.